Negative pole piece structure and lithium ion battery

Abstract

The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a negative pole piece structure and a lithium ion battery. The active material layer is arranged on the surface of the current collector; and the lithium storage layers are arranged on the two sides of the active material layer in the width direction. By optimizing the structure of the pole piece, the problem of lithium precipitation at the edge in the width direction of the pole piece can be solved, and the quality of the battery can be improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery production and manufacturing, and specifically relates to a negative electrode plate structure and a lithium ion battery. Background Art

[0002] As a new type of secondary battery, lithium-ion batteries have the advantages of high energy density and power density, high operating voltage, light weight, small size, long cycle life, good safety, and green environmental protection. They have broad application prospects in portable appliances, power tools, large-scale energy storage, electric transportation power supply, etc.

[0003] In the current lithium-ion battery production process, in order to prevent and slow down the phenomenon of lithium deposition at the edge of the negative electrode of the battery cell, a structure in which the anode electrode is wider than the cathode electrode (overhang) is adopted.

[0004] In the process of realizing the present invention, the inventors found that the prior art has at least the following problems:

[0005] In the actual production of battery cells, considering factors such as the energy density of the battery cells, the overhang margin is insufficient or too small, resulting in lithium deposition at the edge of the electrode when the battery cells are used in harsh environments such as continuous charging and discharging or high temperature, seriously affecting the safety and performance of the battery cells. Utility Model Content

[0006] One of the purposes of the present invention is to address the deficiencies of the prior art and provide a negative electrode plate structure that can solve the problem of lithium deposition at the edge of the plate in the width direction by optimizing the plate structure, thereby helping to improve the quality of the battery.

[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] A negative electrode plate structure comprises a current collector; an active material layer arranged on the surface of the current collector; and a lithium storage layer arranged on both sides of the active material layer in a width direction.

[0009] Preferably, one end of the lithium storage layer extends to the interior of the active material layer, and the other end of the lithium storage layer extends to the outside of the active material layer. The width of the lithium storage layer extending to the interior of the active material layer is x, and the width of the lithium storage layer extending to the outside of the active material layer is y, satisfying the relationship: 1.5mm≤x≤3mm, y≥1.5mm.

[0010] Preferably, the active material layer includes a main body portion and an edge portion, wherein the edge portions are located on both sides of the main body portion in a width direction, and the edge portions cover one end of the lithium storage layer extending into the interior of the active material layer.

[0011] Preferably, the thickness of the main body of the active material layer is equal to the thickness of the lithium storage layer.

[0012] Preferably, the lithium storage layer is divided into two sections, wherein the lithium storage layer of one section is arranged on one side in the width direction of the active material layer, and the lithium storage layer of the other section is arranged on the other side in the width direction of the active material layer, and the lithium storage layers of the two sections are both arranged along the edge of the current collector.

[0013] Preferably, the active material layer has a double-layer structure, which includes a first active material layer and a second active material layer. The first active material layer is arranged on the surface of the current collector, and the second active material layer is arranged on the surface of the first active material layer.

[0014] Preferably, the width of the first active material layer is smaller than that of the second active material layer, and the particle size of the material of the first active material layer is larger than that of the material of the second active material layer.

[0015] Preferably, the width of the active material layer is smaller than the width of the current collector, and the width of the lithium storage layer is smaller than the width of the current collector.

[0016] Preferably, the material of the lithium storage layer is porous manganese oxide or ion sieve type oxide adsorbent.

[0017] A second object of the present invention is to provide a lithium-ion battery comprising the above-mentioned negative electrode plate structure.

[0018] One of the above technical solutions has the following beneficial effects:

[0019] The utility model optimizes the electrode structure and pre-coats a lithium storage layer on the edge of the electrode. The lithium storage layer is made of a material that can absorb lithium. The lithium storage layer can absorb lithium that has not been embedded in the negative electrode in time, which helps to prevent lithium deposition at the edge of the negative electrode in the width direction. At the same time, by adding the lithium storage layer, the overhang margin can be increased, solving the problem of lithium deposition at the edge of the negative electrode due to insufficient overhang. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0021] Figure 1 This is one of the cross-sectional schematic diagrams of the pole piece of the present invention.

[0022] Figure 2 This is the second cross-sectional schematic diagram of the pole piece of the present invention.

[0023] Figure 3 This is the third cross-sectional schematic diagram of the pole piece of the present invention.

[0024] Figure 4 It is a structural schematic diagram of the pole piece of the utility model.

[0025] The description of the accompanying drawings is as follows:

[0026] 1-current collector;

[0027] 2-active material layer; 21-main body; 22-edge portion;

[0028] 3-lithium storage layer;

[0029] 201-first active material layer;

[0030] 202- second active material layer;

[0031] A-width direction;

[0032] x-the width of the lithium storage layer extending to the interior of the active material layer;

[0033] y-the width of the lithium storage layer extending to the outside of the active material layer;

[0034] Y-The lithium storage layer exceeds the width of the active material layer edge. DETAILED DESCRIPTION

[0035] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of the components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0036] Furthermore, the terms “first,” “second,” etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0037] In this utility model, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this utility model based on specific circumstances.

[0038] The present invention will be further described in detail below with reference to the accompanying drawings, but the accompanying drawings are not intended to limit the present invention.

[0039] Example 1

[0040] In the actual production of battery cells, due to factors such as the energy density of the battery cells, the overhang margin is insufficient or too small, resulting in lithium deposition at the edge of the electrode when the battery cells are used in harsh environments such as continuous charging and discharging or high temperature, seriously affecting the safety and performance of the battery cells.

[0041] The negative electrode plate structure of the present invention includes a current collector 1; an active material layer 2, disposed on the surface of the current collector 1; and a lithium storage layer 3, disposed on both sides of the active material layer 2 in the width direction A. By optimizing the plate structure, the present invention pre-coats the edge of the plate with the lithium storage layer 3. The lithium storage layer 3 is made of a material capable of absorbing lithium. The lithium storage layer 3 can absorb lithium that has not been promptly embedded in the negative electrode, helping to prevent lithium deposition at the edge of the negative electrode plate in the width direction. Furthermore, by adding the lithium storage layer 3, the overhang margin can be increased, solving the problem of lithium deposition at the edge of the negative electrode plate due to insufficient overhang.

[0042] In some embodiments, see Figure 1 As shown, the lithium storage layer 3 and the active material layer 2 have the same thickness and are close to each other. A section of the lithium storage layer 3 is located on one side of the width direction A of the active material layer 2. The width of this section of the lithium storage layer 3 can be understood as the width of the lithium storage layer 3 exceeding the edge of the active material layer 2. The width of the lithium storage layer 3 exceeding the edge of the active material layer 2 is Y, and Y ≥ 1.5 mm. This ensures that after the electrode is cut, the edge of each electrode is coated with the lithium storage layer 3. In other embodiments, see Figure 2 As shown, a lithium storage layer 3 is pre-coated on the edge of the electrode, and the cross-section of the lithium storage layer 3 is designed to be trapezoidal as a whole. Then, the active material layer 2 is coated so that one end of the lithium storage layer 3 extends to the interior of the active material layer 2. One end of the lithium storage layer 3 is roughly a right triangle, and the edge portion 22 of the active material layer 2 is roughly an inverted direct triangle, which can cooperate with one end of the lithium storage layer 3 so that the edge portion 22 of the active material layer 2 just overlaps the surface of one end of the lithium storage layer 3, that is, the active material layer 2 as a whole is flush with the lithium storage layer 3, avoiding the appearance of steps on the surface of the electrode, causing the battery cell to be uneven and lithium deposition to occur.

[0043] It should be noted that overhang refers to the excess width of the negative electrode sheet compared to the positive electrode sheet. The current collector 1 preferably uses copper foil as the negative electrode current collector. The present invention first coats the copper foil with a lithium storage layer 3, with the coating position roughly at the edge of the active material layer 2. The treated copper foil is then coated with an active material slurry to form the active material layer 2. The width of the lithium storage layer 3 extending into the active material layer 2 is x, and the width of the lithium storage layer 3 extending outside the active material layer 2 is y, satisfying the relationship: 1.5mm≤x≤3mm, y≥1.5mm. The width of the lithium storage layer 3 extending into the active material layer 2 can be understood as the overlap area between the active material layer 2 and the lithium storage layer 3. The width x of the lithium storage layer 3 extending into the active material layer 2 can be 1.5mm, 2mm, 2.5mm, 3mm, etc. This prevents the width from being too small, resulting in insufficient overhang and lithium deposition at the edge of the negative electrode sheet, which is not conducive to reducing the risk of lithium deposition in the battery. At the same time, it prevents the width from being too large, which affects the coating amount of active material and causes a loss of battery energy density. The width y of the lithium storage layer 3 extending to the outside of the active material layer 2 can be 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, etc., to ensure that the edge of each electrode is coated with the lithium storage layer 3 after the electrode is cut. In addition, limiting the width of the extension of the lithium storage layer 3 takes into account both the energy density of the battery and the reduction of the risk of lithium plating in the battery, which helps to improve the quality of the battery. Specifically, in this embodiment, the lithium storage layer 3 is first coated on a preset position of the copper foil, and the coating width of the lithium storage layer 3 is 4mm. Then, the active material slurry is coated on the treated copper foil, wherein the width of the lithium storage layer 3 extending to the inside of the active material layer 2 is 2mm, that is, the width of the overlapping area between the active material layer 2 and the lithium storage layer 3 is 2mm, and the width of the lithium storage layer 3 extending to the outside of the active material layer 2 is 2mm, that is, the lithium storage layer 3 exceeds the width of the active material layer 2 by 2mm.

[0044] In the negative electrode sheet structure according to the present invention, the active material layer 2 includes a main portion 21 and an edge portion 22. The edge portions 22 are located on both sides of the main portion 21 in the width direction A. The edge portion 22 covers one end of the lithium storage layer 3 extending into the interior of the active material layer 2. In this embodiment, the main portion 21 is roughly located between the two sections of the lithium storage layer 3. The main portion 21 and the lithium storage layer 3 are both located on the same surface of the current collector 1. The thickness of the main portion 21 is equal to the thickness of the lithium storage layer 3. The edge portion 22 covers the upper surface of the lithium storage layer 3. Since the lithium storage layer 3 is first coated on the copper foil and then the active material slurry is coated on the copper foil, one end of the lithium storage layer 3 can extend into the interior of the active material layer 2. It can also be understood that the edge portion 22 overlaps the upper surface of the lithium storage layer 3.

[0045] In the negative electrode sheet structure according to the present invention, the lithium storage layer 3 is divided into two sections, one section of the lithium storage layer 3 is arranged on one side of the active material layer 2 in the width direction A, and the other section of the lithium storage layer 3 is arranged on the other side of the active material layer 2 in the width direction A. Both sections of the lithium storage layer 3 are arranged along the edge of the current collector 1. In this embodiment, the two sections of the lithium storage layer 3 are roughly strip-shaped, the width of the active material layer 2 is smaller than the width of the current collector 1, the width of the lithium storage layer 3 is smaller than the width of the current collector 1, and the width of the two sections of the lithium storage layer 3 is smaller than the width of the main portion 21 of the active material layer 2. The two sections of the lithium storage layer 3 are pre-coated on both sides of the active material layer 2 in the width direction A, and then the active material is coated on the empty foil area of ​​the current collector 1 between the two sections of the lithium storage layer 3. Part of the active material overlaps the upper surface of the lithium storage layer 3, which can absorb lithium that has not been embedded in the negative electrode in time, helping to prevent lithium deposition at the edge of the negative electrode sheet in the width direction.

[0046] In some embodiments, the active material layer 2 has a double-layer structure, comprising a first active material layer 201 and a second active material layer 202. The first active material layer 201 is disposed on the surface of the current collector 1, and the second active material layer 202 is disposed on the surface of the first active material layer 201. Specifically, the active material layer 2 is coated in a double layer, with the lithium storage layer 3 pre-coated on both sides of the active material layer 2 in the width direction A. The first active material layer 201 and the second active material layer 202 are then sequentially coated, such that the lithium storage layer 3 extends into the interiors of the first and second active material layers 201 and 202. Specifically, after coating the first active material layer 201, the edge of the first active material layer 201 covers a portion of the lithium storage layer 3, forming an overlapping region with the edge of the first active material layer 201 and the lithium storage layer 3. After coating the second active material layer 202, the edge of the second active material layer 202 covers a portion of the lithium storage layer 3, forming an overlapping region with the edge of the second active material layer 202 and the lithium storage layer 3. In addition, the width of the first active material layer 201 is smaller than the width of the second active material layer 202, so that the second active material layer 202 completely covers the first active material layer 201. The material particle size of the first active material layer 201 is larger than the material particle size of the second active material layer 202. The first active material layer 201 is located at the bottom layer and uses large-particle active materials, and has the characteristics of high compaction. The second active material layer 202 is located on the surface layer and uses small-particle active materials, and has a fast charging function.

[0047] In the negative electrode plate structure according to the present invention, the material of the lithium storage layer 3 is porous manganese oxide or ion sieve type oxide adsorbent, but the present invention is not limited thereto and other materials that adsorb lithium can also be used, which is not limited here.

[0048] The working principle of this utility model is:

[0049] The utility model optimizes the electrode structure and pre-coats a lithium storage layer 3 on the edge of the electrode. The lithium storage layer 3 is made of a material that can absorb lithium. The lithium storage layer 3 can absorb lithium that has not been embedded in the negative electrode in time, which helps to prevent lithium deposition at the edge of the negative electrode in the width direction. At the same time, by adding the lithium storage layer 3, the overhang margin can be increased, solving the problem of lithium deposition at the edge of the negative electrode due to insufficient overhang.

[0050] lithium-ion batteries

[0051] The battery includes a first electrode, a diaphragm and a second electrode, which are wound in sequence to form a bare cell.

[0052] The first pole piece and the second pole piece of the battery are respectively provided with pole tabs, and the positions of the two sets of pole tabs correspond to the positive pole and the negative pole of the battery.

[0053] In order to avoid short circuit between the positive and negative pole pieces, a diaphragm is provided between each two adjacent pole pieces, and the pole pieces with opposite polarities are electrically isolated by the diaphragm.

[0054] The first electrode piece can be a positive electrode piece, and the second electrode piece can be a negative electrode piece; or, the first electrode piece can be a negative electrode piece, and the second electrode piece can be a positive electrode piece, which is not limited here. The negative electrode piece adopts the above-mentioned electrode piece structure, which can solve the problem of lithium deposition at the edge of the electrode piece in the width direction, and helps to improve the quality of the battery.

[0055] Example 2

[0056] The difference from Example 1 is that in this embodiment, the lithium storage layer 3 is first coated on a preset position of the copper foil, and the coating width of the lithium storage layer 3 is 2 mm. Then, the active material slurry is coated on the treated copper foil, wherein the width of the lithium storage layer 3 extending to the inside of the active material layer 2 is 1 mm, that is, the width of the overlapping area between the active material layer 2 and the lithium storage layer 3 is 1 mm, and the width of the lithium storage layer 3 extending to the outside of the active material layer 2 is 1 mm, that is, the lithium storage layer 3 exceeds the width of the active material layer 2 by 1 mm.

[0057] The other structures are the same as those in the first embodiment and will not be described again here.

[0058] Comparative Example 1

[0059] In this embodiment, the lithium storage layer 3 is not coated, and then the active material slurry is coated on the copper foil to form an active material layer on the surface of the current collector 1.

[0060] The battery cells made of the negative electrode sheets of Example 1, Example 2 and Comparative Example 1 were disassembled after being used in the same environment for a preset time.

[0061] The lithium deposition at the edge of the electrode of the battery cells of Examples 1 and 2 is better than that of the electrode of the battery cell of Comparative Example 1. In particular, the electrode of the battery cell of Comparative Example 1 has obvious purple spots and lithium deposition at the width direction of the electrode, while the electrode of the battery cell of Example 2 has slight lithium deposition at the width direction of the electrode. The electrode of the battery cell of Example 2 has basically no purple spots and no lithium deposition at the width direction of the electrode, indicating that the present invention pre-coats the edge of the electrode with a lithium storage layer 3. The lithium storage layer 3 is made of a material that can absorb lithium. The lithium storage layer 3 can absorb lithium that is not embedded in the negative electrode in time, which helps to prevent lithium deposition at the width direction of the negative electrode. At the same time, by adding the lithium storage layer 3, the overhang margin can be increased, solving the problem of lithium deposition at the edge of the negative electrode due to insufficient overhang. In addition, the width of the lithium storage layer 3 of Example 1 is within a preset range, taking into account both the energy density of the battery and reducing the risk of lithium deposition, which helps to improve the quality of the battery.

[0062] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are for convenience only and do not constitute any limitation on the present invention.

Claims

1. A negative electrode plate structure, characterized in that: include: current collector(1); an active material layer (2) disposed on the surface of the current collector (1); The lithium storage layer (3) is arranged on both sides of the active material layer (2) in the width direction.

2. The negative electrode plate structure according to claim 1, wherein: One end of the lithium storage layer (3) extends to the interior of the active material layer (2), and the other end of the lithium storage layer (3) extends to the outside of the active material layer (2). The width of the lithium storage layer (3) extending to the interior of the active material layer (2) is x, and the width of the lithium storage layer (3) extending to the outside of the active material layer (2) is y, satisfying the relationship: 1.5 mm ≤ x ≤ 3 mm, y ≥ 1.5 mm.

3. The negative electrode plate structure according to claim 2, wherein: The active material layer (2) comprises a main body portion (21) and an edge portion (22), wherein the edge portion (22) is located on both sides of the main body portion (21) in a width direction, and the edge portion (22) covers one end of the lithium storage layer (3) extending into the interior of the active material layer (2).

4. The negative electrode plate structure according to claim 3, wherein: The thickness of the main portion (21) of the active material layer (2) is equal to the thickness of the lithium storage layer (3).

5. The negative electrode plate structure according to claim 4, characterized in that: The lithium storage layer (3) is divided into two sections, wherein the lithium storage layer (3) of one section is arranged on one side in the width direction of the active material layer (2), and the lithium storage layer (3) of the other section is arranged on the other side in the width direction of the active material layer (2), and the lithium storage layer (3) of the two sections are both arranged along the edge of the current collector (1).

6. A negative electrode plate structure according to any one of claims 1 to 5, characterized in that: The active material layer (2) is a double-layer structure, comprising a first active material layer (201) and a second active material layer (202), wherein the first active material layer (201) is arranged on the surface of the current collector (1), and the second active material layer (202) is arranged on the surface of the first active material layer (201).

7. The negative electrode plate structure according to claim 6, characterized in that: The width of the first active material layer (201) is smaller than the width of the second active material layer (202), and the particle size of the material of the first active material layer (201) is larger than the particle size of the material of the second active material layer (202).

8. A negative electrode plate structure according to any one of claims 1 to 5, characterized in that: The width of the active material layer (2) is smaller than the width of the current collector (1), and the width of the lithium storage layer (3) is smaller than the width of the current collector (1).

9. A negative electrode plate structure according to any one of claims 1 to 5, characterized in that: The material of the lithium storage layer (3) is porous manganese oxide or ion sieve type oxide adsorbent.

10. A lithium-ion battery, characterized in that: The negative electrode plate structure comprises the negative electrode plate structure according to any one of claims 1 to 9.

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